To increase mechanical strength, a gas diffusion electrode substrate in a fuel cell conventionally uses a porous electrode substrate, which is a sheet-type carbon-carbon composite made by forming short carbon fibers into a sheet, binding the fibers together with an organic polymer and sintering at high temperature to carbonize the organic polymer (see patent publication 1).
In addition, to enhance the conductivity of the above substrate, a type of substrate made by adding carbon powder to a carbonizable resin is proposed (see patent publication 2).
Moreover, to lower the cost, a porous electrode substrate is proposed, where a short oxidized fiber sheet is formed and sintered at high temperature to carbonize the short oxidized fibers (see patent publication 3).
Also proposed is a fuel cell gas diffusion layer formed with a mat containing multiple carbon fibers and multiple acrylic pulp fibers, which are incorporated into the carbon-fiber mat, cured and carbonized after being incorporated into the carbon-fiber mat (see patent publication 4).
To lower the cost, also proposed is a method for manufacturing a non-carbonized porous electrode substrate in which short carbon fibers are bound to each other by split fibers containing fibrillated portions made of a conductive substance and a water-repellent substance with a contact angle of 80 degrees or greater.